How to add roughness to a surface using modifiers?
Yes, though you'll probably want to use two for maximum effect; I recommend applying a Subdivision surface modifier ('Simple', not 'Catmull-Clark'), and then applying a Displace modifier. If your geometry is sufficiently complex it should work fine.

The Subdivision Surface modifier adds vertices to your mesh, then the Displace modifier uses those vertices to add the roughness you're looking for.

Before Modifiers


After Modifiers


You can, of course, use different settings for the Displace texture if you want to achieve different kinds of roughness.